DevTools: Restore CodeMirror cm-s-default theme

These were accidentally removed in crrev.com/512716 and broke C++
syntax highlighting.

Change-Id: Ic86ad294792aa2b1f11c5e40812ebefd07f3b6de
Reviewed-on: https://chromium-review.googlesource.com/762103Reviewed-by: Andrey Lushnikov <lushnikov@chromium.org>
Commit-Queue: Andrey Lushnikov <lushnikov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#515435}

third_party/WebKit/Source/devtools/front_end/ui/inspectorSyntaxHighlight.css

@@ -140,3 +140,26 @@
 .cm-strikethrough {text-decoration: line-through;}
 
 .cm-invalidchar {color: #f00;}
+
+.cm-s-default .cm-header {color: blue;}
+.cm-s-default .cm-quote {color: #090;}
+
+.cm-s-default .cm-keyword {color: #708;}
+.cm-s-default .cm-atom {color: #219;}
+.cm-s-default .cm-number {color: #164;}
+.cm-s-default .cm-def {color: #00f;}
+.cm-s-default .cm-variable-2 {color: #05a;}
+.cm-s-default .cm-variable-3, .cm-s-default .cm-type {color: #085;}
+.cm-s-default .cm-comment {color: #a50;}
+.cm-s-default .cm-string {color: #a11;}
+.cm-s-default .cm-string-2 {color: #f50;}
+.cm-s-default .cm-meta {color: #555;}
+.cm-s-default .cm-qualifier {color: #555;}
+.cm-s-default .cm-builtin {color: #30a;}
+.cm-s-default .cm-bracket {color: #997;}
+.cm-s-default .cm-tag {color: #170;}
+.cm-s-default .cm-attribute {color: #00c;}
+.cm-s-default .cm-hr {color: #999;}
+.cm-s-default .cm-link {color: #00c;}
+
+.cm-s-default .cm-error {color: #f00;}